As a plasma processing apparatus for performing a plasma process on substrates such as semiconductor wafers, an apparatus including: a loader module maintained in an atmospheric pressure environment to load and unload semiconductor wafers into and from a FOUP that is a container having a plurality of semiconductor wafers accommodated therein between a load port for mounting the FOUP and a processing module (vacuum processing chamber) for performing a plasma process on semiconductor wafers; a transfer module maintained in a vacuum environment to load and unload semiconductor wafers into and from the processing module; and a load lock module disposed between the loader module and the transfer module and being selectively switchable between the atmospheric pressure environment and the vacuum environment has been used. In such a plasma processing apparatus, a first wafer transfer unit is disposed in the loader module, and a second wafer transfer unit is disposed in the transfer module. The wafer transfer units transfer semiconductor wafers between the load port and the processing module.
As the wafer transfer unit, a unit configured to have an extendable arm and be entirely rotatable has been used. In such a wafer transfer unit, an operation of the wafer transfer unit is controlled based on detection information obtained by individually detecting, using sensors, information on a rotating operation, an extending/contracting operation of the extendable arm, information on the presence or not of a semiconductor wafer on the extendable arm, information on an opening/closing operation of gate values between the respective modules, and the like.
Specifically, after the contracting operation of the extendable arm holding a semiconductor wafer taken out from a vacuum transfer chamber is terminated, the wafer transfer unit initiates a transfer operation of the held semiconductor wafer toward the load lock module. Also, the closing operation of a gate valve for allowing the vacuum transfer chamber to be isolated from and communicate with the transfer module is initiated after the information on the contracting operation of the extendable arm and the presence or not of the semiconductor wafer is confirmed (e.g., see Patent Document 1).